1. Field of the Invention
The present invention relates to a plasma processing device.
2. Description of the Related Art
In the case of the plasma processing device such as plasma etching and CVD devices, an object to be processed is mounted on a mount in the plasma process vessel and plasma-processed while keeping the object clamped at the peripheral rim thereof between a clamping member and the mount.
In the case of the plasma etching device, for example, a semiconductor wafer 72 to be processed is mounted on the top of a lower electrode 70 which is opposed to an upper electrode (not shown), and it is fixed there by clamping its peripheral rim between a clamping member 74 and the lower electrode 70, as shown in FIG. 1A. When it is to be carried out of and into the plasma process vessel, rods 76 related to the clamping member 74 are extended to lift the clamping member 74 so as to release it from its clamped state, as shown in FIG. 1B.
The wafer 72 to be processed is usually exposed to plasma in the plasma process vessel. Charge is thus stored in it during the plasma process. In short, it is charged up.
When the clamping member 74 is lifted, as shown in FIG. 1B, to release the wafer 72 from its clamped state after this plasma process is finished, the semiconductor wafer 72 thus charged up adheres electro-statically to the clamping member 74. The wafer 72 must remain on the top of the lower electrode 70, as shown by a solid line in FIG. 1B, after it is released from its clamped state, but it is sometimes lifted together with the clamping member 74, as shown by a two-dot and dash line in FIG. 1B, electrostatically adhering to the clamping member 74. When it is lifted together with the clamping member 74 in this manner, it becomes impossible to carry it out of the plasma process vessel and set a new one there. This makes it necessary for the operator to